Low-leakage asymmetric-cell SRAM

摘要

We introduce a novel family of asymmetric dual-Vt static random access memory cell designs that reduce leakage power in caches while maintaining low access latency. Our designs exploit the strong bias toward zero at the bit level exhibited by the memory value stream of ordinary programs. Compared to conventional symmetric high-performance cells, our cells offer significant leakage reduction in the zero state and, in some cases, also in the one state, albeit to a lesser extent. A novel sense amplifier, in combination with dummy bitlines, allows for read times to be on par with conventional symmetric cells. With one cell design, leakage is reduced by 7× (in the zero state) with no performance degradation, but with a stability degradation of 6%. Another cell design reduces leakage by 2× (in the zero state) with no performance or stability loss. An alternative cell design reduces leakage by 58× (in the zero state) with a performance degradation of 1% and an area increase of 2.4% and no stability degradation.